Have a look at the potato day threads. If you're anywhere near Hampshire then the potato day price this year was 12p/tuber (20p for Sarpo). Likely to be similar or only 1-2p more at the next one.
They work out a LOT cheaper than the sent ones if you're nearby or even not so near. I'm 90 miles from Ryton and so that's about £18 in petrol return: I share driving with a lottie friend and so it's effectively £9 a year. Postage on potatoes is around £5 so I'm only £4 down if I share a car, with that being recouped straightaway on tuber prices, with the advantage of not having to waste tubers by buying too many in order to get more than one variety. And it's a fun day out.
moonbells